Method and apparatus for encoding video by using deblocking filtering, and method and apparatus for decoding video by using deblocking filtering

ABSTRACT

A method and apparatus for encoding video by using deblocking filtering, and a method and apparatus for decoding video by using deblocking filtering are provided. The method of encoding video includes: splitting a picture into a maximum coding unit; determining coding units of coded depths and encoding modes for the coding units of the maximum coding unit by prediction encoding the coding units of the maximum coding unit based on at least one prediction unit and transforming the coding units based on at least one transformation unit, wherein the maximum coding unit is hierarchically split into the coding units as a depth deepens, and the coded depths are depths where the maximum coding unit is encoded in the coding units; and performing deblocking filtering on video data being inversely transformed into a spatial domain in the coding units, in consideration of the encoding modes.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This is a Continuation application of U.S. application Ser. No.14/307,096, filed Jun. 17, 2014, which is a Continuation application ofU.S. application Ser. No. 13/006,078, now U.S. Pat. No. 8,792,561, filedJan. 13, 2011, which claims priority from Korean Patent Application No.10-2010-0003559, filed on Jan. 14, 2010 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

The exemplary embodiments relate to encoding and decoding video.

2. Description of the Related Art

As hardware for reproducing and storing high resolution or high qualityvideo content is being developed and supplied, there is an increasingneed for a video codec for effectively encoding or decoding the highresolution or high quality video content. In a related art video codec,video is encoded according to a limited encoding method based on amacroblock having a predetermined size.

SUMMARY

One or more exemplary embodiments provide deblocking filtering performedin consideration of boundaries between various data units to be used inencoding and decoding processes, and video encoding and decoding usingthe deblocking filtering.

According to an aspect of an exemplary embodiment, there is provided amethod of encoding video by using deblocking filtering, the methodincluding: splitting a picture into a maximum coding unit; determiningcoding units of coded depths and encoding modes for the coding units ofthe maximum coding unit by prediction encoding the coding units of themaximum coding unit on the basis of at least one prediction unit andtransforming the coding units on the basis of at least onetransformation unit, wherein the maximum coding unit is hierarchicallysplit into the coding units as a depth deepens, and the coded depths aredepths where the maximum coding unit is encoded in the coding units; andperforming deblocking filtering on video data being inverselytransformed into a spatial domain in the coding units, in considerationof the determined encoding modes of the coding units.

The coding unit may be characterized by a maximum size and a depth.

The depth denotes the number of times a coding unit is hierarchicallysplit, and as the depth deepens, deeper coding units according to depthsmay be split from the maximum coding unit to obtain minimum codingunits. The depth is deepened from an upper depth to a lower depth. Asthe depth deepens, the number of times the maximum coding unit is splitincreases, and a total number of possible times the maximum coding unitis split corresponds to a maximum depth. The maximum size and themaximum depth of the coding unit may be pre-determined.

According to an aspect of another exemplary embodiment, there isprovided a method of decoding video by using deblocking filtering, themethod including: parsing a received bitstream to extract encoding modesof coding units and video data encoded in the coding units; producingtransformation coefficients of the coding units by entropy decoding andinversely quantizing the encoded video data; reconstructing video datain a spatial domain by inversely transforming the transformationcoefficients on the basis of a transformation unit and predictiondecoding the transformation coefficients on the basis of a predictionunit, according to the encoding modes of the coding unit; and performingdeblocking filtering on the video data in the spatial domain, inconsideration of the encoding modes of the coding units.

The performing the deblocking filtering may include performing thedeblocking filtering on boundaries of prediction units or transformationunits corresponding to the coding units of the video data in the spatialdomain, in consideration of the encoding modes of the coding units.

The performing the deblocking filtering may include performing thedeblocking filtering in consideration of whether current boundaries areboundaries of at least one from among the coding units, predictionunits, and transformation units, which are defined in the encoding modesof the coding units.

The performing the deblocking filtering may include performing thedeblocking filtering in consideration of at least one from among thesizes of the coding units, sizes of the prediction units, and sizes ofthe prediction units according to the encoding modes of the codingunits. The performing the deblocking filtering may include performingthe deblocking filtering in consideration of partition types of thecoding units according to the encoding modes of the coding units. Thepartition types may include a symmetrical partition type and anasymmetrical partition type.

The performing the deblocking filtering may include performing thedeblocking filtering in consideration of a prediction mode of theprediction units, whether an encoded residual component exists, a motionvector, a number of reference pictures, and an index of the referencepictures, which are defined in the encoding modes of the coding units.

The performing the deblocking filtering may include determining aboundary strength in consideration of the encoding modes of the codingunits, determining whether deblocking filtering is to be performed, ordetermining a deblocking filtering method including informationregarding filter tab size.

According to an aspect of another exemplary embodiment, there isprovided an apparatus for encoding video by using deblocking filtering,the apparatus including: a maximum coding unit splitter which splits apicture into a maximum coding unit; a coding unit and encoding modedeterminer which determines coding units of coded depths and encodingmodes for the coding units by prediction encoding the coding units ofthe maximum coding unit on the basis of at least one prediction unit andtransforming the coding units on the basis of at least onetransformation unit, wherein the maximum coding unit is hierarchicallysplit into the coding units as a depth deepens and the coded depths aredepths where the maximum coding unit is encoded in the coding units; anda deblocking filtering performing unit which performs deblockingfiltering on video data being inversely transformed into a spatialdomain in the coding units, in consideration of the determined encodingmodes of the coding units.

According to an aspect of another exemplary embodiment, there isprovided an apparatus for decoding video by using deblocking filtering,the apparatus including: a data extractor which parses a receivedbitstream to extract encoding modes of coding units and video dataencoded in the coding units; an entropy decoding and inversequantization unit which produces transformation coefficients of thecoding units by entropy decoding and inversely quantizing the encodedvideo data; an inverse transformation and prediction decoding unit whichreconstructs video data in a spatial domain by inversely transformingthe transformation coefficients on the basis of a transformation unitand prediction decoding the transformation coefficients on the basis ofa prediction unit, according to the encoding modes of the coding unit;and a deblocking filtering performing unit which performs deblockingfiltering on the video data in the spatial domain, in consideration ofthe encoding modes of the coding units.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon aprogram for executing the method of encoding video by using deblockingfiltering.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon aprogram for executing the method of decoding video by using deblockingfiltering.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become more apparent by describingin detail exemplary embodiments thereof with reference to the attacheddrawings in which:

FIG. 1 is a block diagram of an apparatus for encoding a video,according to an exemplary embodiment;

FIG. 2 is a block diagram of an apparatus for decoding a video,according to an exemplary embodiment;

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment;

FIG. 4 is a block diagram of an image encoder based on coding unitsaccording to an exemplary embodiment;

FIG. 5 is a block diagram of an image decoder based on coding unitsaccording to an exemplary embodiment;

FIG. 6 is a diagram illustrating deeper coding units according todepths, and partitions according to an exemplary embodiment of thepresent invention;

FIG. 7 is a diagram for describing a relationship between a coding unitand transformation units, according to an exemplary embodiment;

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment;

FIG. 9 is a diagram of deeper coding units according to depths,according to an exemplary embodiment;

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units, prediction units, and transformation units, according toan exemplary embodiment;

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information of Table 1;

FIG. 14 is a flowchart illustrating a method of encoding a video,according to an exemplary embodiment;

FIG. 15 is a flowchart illustrating a method of decoding a video,according to an exemplary embodiment;

FIG. 16 is a block diagram of a video encoding apparatus employingdeblocking filtering, according to an exemplary embodiment;

FIG. 17 is a block diagram of a video decoding apparatus employingdeblocking filtering, according to an exemplary embodiment;

FIG. 18 is a block diagram for describing a relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment;

FIG. 19 is a block diagram for describing a relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment;

FIG. 20 is a block diagram for describing a relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment;

FIG. 21 illustrates a method of determining a deblocking filteringmethod, according to an exemplary embodiment;

FIG. 22 illustrates samples that are to be deblocking filtered,according to an exemplary embodiment;

FIG. 23 is a flowchart illustrating a method of encoding video by usingdeblocking filtering, according to an exemplary embodiment; and

FIG. 24 is a flowchart illustrating a method of decoding video by usingdeblocking filtering, according to an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a video encoding apparatus, a video decoding apparatus, amethod of encoding video, and a method of decoding video according toexemplary embodiments will be described in detail with reference toFIGS. 1 to 24. Specifically, encoding and decoding video on the basis ofspatially hierarchical data units according to exemplary embodimentswill be described with reference to FIGS. 1 through 15. Also, encodingand decoding video by performing deblocking filtering in considerationof coding units, prediction units, and transformation units, accordingto exemplary embodiments, will be described with reference to FIGS. 16through 24.

In this disclosure, a ‘coding unit’ means an encoding data unit in whichimage data is encoded at an encoder side, and an encoded data unit inwhich the encoded image data is decoded at a decoder side. Also, a‘coded depth’ means a depth where a coding unit is encoded. Furthermore,an ‘image’ may denote a still image for a video or a moving image, thatis, the video itself.

FIG. 1 is a block diagram of a video encoding apparatus 100 according toan exemplary embodiment. The video encoding apparatus 100 includes amaximum coding unit splitter 110, a coding unit determiner 120, and anoutput unit 130.

The maximum coding unit splitter 110 may split a current picture basedon a maximum coding unit for the current picture of an image. If thecurrent picture is larger than the maximum coding unit, image data ofthe current picture may be split into the at least one maximum codingunit. The maximum coding unit according to an exemplary embodiment maybe a data unit having a size of 32×32, 64×64, 128×128, 256×256, etc.,wherein a shape of the data unit is a square having a width and lengthin squares of 2. The image data may be output to the coding unitdeterminer 120 according to the at least one maximum coding unit.

A coding unit according to an exemplary embodiment may be characterizedby a maximum size and a depth. The depth denotes a number of times thecoding unit is spatially split from the maximum coding unit, and as thedepth deepens or increases, deeper encoding units according to depthsmay be split from the maximum coding unit to a minimum coding unit. Adepth of the maximum coding unit is an uppermost depth and a depth ofthe minimum coding unit is a lowermost depth. Since a size of a codingunit corresponding to each depth decreases as the depth of the maximumcoding unit deepens, a coding unit corresponding to an upper depth mayinclude a plurality of coding units corresponding to lower depths.

As described above, the image data of the current picture is split intothe maximum coding units according to a maximum size of the coding unit,and each of the maximum coding units may include deeper coding unitsthat are split according to depths. Since the maximum coding unitaccording to an exemplary embodiment is split according to depths, theimage data of a spatial domain included in the maximum coding unit maybe hierarchically classified according to depths.

A maximum depth and a maximum size of a coding unit, which limit thetotal number of times a height and a width of the maximum coding unitare hierarchically split, may be predetermined.

The coding unit determiner 120 encodes at least one split regionobtained by splitting a region of the maximum coding unit according todepths, and determines a depth to output a finally encoded image dataaccording to the at least one split region. In other words, the codingunit determiner 120 determines a coded depth by encoding the image datain the deeper coding units according to depths, according to the maximumcoding unit of the current picture, and selecting a depth having theleast encoding error. Thus, the encoded image data of the coding unitcorresponding to the determined coded depth is finally output. Also, thecoding units corresponding to the coded depth may be regarded as encodedcoding units.

The determined coded depth and the encoded image data according to thedetermined coded depth are output to the output unit 130.

The image data in the maximum coding unit is encoded based on the deepercoding units corresponding to at least one depth equal to or below themaximum depth, and results of encoding the image data are compared basedon each of the deeper coding units. A depth having the least encodingerror may be selected after comparing encoding errors of the deepercoding units. At least one coded depth may be selected for each maximumcoding unit.

The size of the maximum coding unit is split as a coding unit ishierarchically split according to depths, and as the number of codingunits increases. Also, even if coding units correspond to same depth inone maximum coding unit, it is determined whether to split each of thecoding units corresponding to the same depth to a lower depth bymeasuring an encoding error of the image data of the each coding unit,separately. Accordingly, even when image data is included in one maximumcoding unit, the image data is split to regions according to the depthsand the encoding errors may differ according to regions in the onemaximum coding unit, and thus the coded depths may differ according toregions in the image data. Thus, one or more coded depths may bedetermined in one maximum coding unit, and the image data of the maximumcoding unit may be divided according to coding units of at least onecoded depth.

Accordingly, the coding unit determiner 120 may determine coding unitshaving a tree structure included in the maximum coding unit. The ‘codingunits having a tree structure’ according to an exemplary embodimentinclude coding units corresponding to a depth determined to be the codeddepth, from among all deeper coding units included in the maximum codingunit. A coding unit of a coded depth may be hierarchically determinedaccording to depths in the same region of the maximum coding unit, andmay be independently determined in different regions. Similarly, a codeddepth in a current region may be independently determined from a codeddepth in another region.

A maximum depth according to an exemplary embodiment is an index relatedto the number of splitting times from a maximum coding unit to a minimumcoding unit. A first maximum depth according to an exemplary embodimentmay denote the total number of splitting times from the maximum codingunit to the minimum coding unit. A second maximum depth according to anexemplary embodiment may denote the total number of depth levels fromthe maximum coding unit to the minimum coding unit. For example, when adepth of the maximum coding unit is 0, a depth of a coding unit, inwhich the maximum coding unit is split once, may be set to 1, and adepth of a coding unit, in which the maximum coding unit is split twice,may be set to 2. Here, if the minimum coding unit is a coding unit inwhich the maximum coding unit is split four times, 5 depth levels ofdepths 0, 1, 2, 3 and 4 exist, and thus the first maximum depth may beset to 4, and the second maximum depth may be set to 5.

Prediction encoding and transformation may be performed according to themaximum coding unit. The prediction encoding and the transformation arealso performed based on the deeper coding units according to a depthequal to or depths less than the maximum depth, according to the maximumcoding unit. Transformation may be performed according to method oforthogonal transformation or integer transformation.

Since the number of deeper coding units increases whenever the maximumcoding unit is split according to depths, encoding including theprediction encoding and the transformation is performed on all of thedeeper coding units generated as the depth deepens. For convenience ofdescription, the prediction encoding and the transformation will now bedescribed based on a coding unit of a current depth, in a maximum codingunit.

The video encoding apparatus 100 may variably select a size or shape ofa data unit for encoding the image data. In order to encode the imagedata, operations, such as prediction encoding, transformation, andentropy encoding, are performed, and at this time, the same data unitmay be used for all operations or different data units may be used foreach operation.

For example, the video encoding apparatus 100 may select not only acoding unit for encoding the image data, but also a data unit differentfrom the coding unit so as to perform the prediction encoding on theimage data in the coding unit.

In order to perform prediction encoding in the maximum coding unit, theprediction encoding may be performed based on a coding unitcorresponding to a coded depth, i.e., based on a coding unit that is nolonger split to coding units corresponding to a lower depth.Hereinafter, the coding unit that is no longer split and becomes a basisunit for prediction encoding will now be referred to as a ‘predictionunit’. A partition obtained by splitting the prediction unit may includea prediction unit or a data unit obtained by splitting at least one of aheight and a width of the prediction unit.

For example, when a coding unit of 2N×2N (where N is a positive integer)is no longer split and becomes a prediction unit of 2N×2N, and a size ofa partition may be 2N×2N, 2N×N, N×2N, or N×N. Examples of a partitiontype include symmetrical partitions that are obtained by symmetricallysplitting a height or width of the prediction unit, partitions obtainedby asymmetrically splitting the height or width of the prediction unit,such as 1:n or n:1, partitions that are obtained by geometricallysplitting the prediction unit, and partitions having arbitrary shapes.

A prediction mode of the prediction unit may be at least one of an intramode, a inter mode, and a skip mode. For example, the intra mode or theinter mode may be performed on the partition of 2N×2N, 2N×N, N×2N, orN×N. Also, the skip mode may be performed only on the partition of2N×2N. The encoding is independently performed on one prediction unit ina coding unit, thereby selecting a prediction mode having a leastencoding error.

The video encoding apparatus 100 may also perform the transformation onthe image data in a coding unit based not only on the coding unit forencoding the image data, but also based on a data unit that is differentfrom the coding unit.

In order to perform the transformation in the coding unit, thetransformation may be performed based on a data unit having a sizesmaller than or equal to the coding unit. For example, the data unit forthe transformation may include a data unit for an intra mode and a dataunit for an inter mode.

A data unit used as a base of the transformation will now be referred toas a ‘transformation unit’. A transformation depth indicating the numberof splitting times to reach the transformation unit by splitting theheight and width of the coding unit may also be set in thetransformation unit. For example, in a current coding unit of 2N×2N, atransformation depth may be 0 when the size of a transformation unit isalso 2N×2N, may be 1 when each of the height and width of the currentcoding unit is split into two equal parts, totally split into 4¹transformation units, and the size of the transformation unit is thusN×N, and may be 2 when each of the height and width of the currentcoding unit is split into four equal parts, totally split into 4²transformation units and the size of the transformation unit is thusN/2×N/2. For example, the transformation unit may be set according to ahierarchical tree structure, in which a transformation unit of an uppertransformation depth is split into four transformation units of a lowertransformation depth according to the hierarchical characteristics of atransformation depth.

Similarly to the coding unit, the transformation unit in the coding unitmay be recursively split into smaller sized regions, so that thetransformation unit may be determined independently in units of regions.Thus, residual data in the coding unit may be divided according to thetransformation having the tree structure according to transformationdepths.

Encoding information according to coding units corresponding to a codeddepth requires not only information about the coded depth, but alsoabout information related to prediction encoding and transformation.Accordingly, the coding unit determiner 120 not only determines a codeddepth having a least encoding error, but also determines a partitiontype in a prediction unit, a prediction mode according to predictionunits, and a size of a transformation unit for transformation.

Coding units according to a tree structure in a maximum coding unit anda method of determining a partition, according to exemplary embodiments,will be described in detail later with reference to FIGS. 3 through 12.

The coding unit determiner 120 may measure an encoding error of deepercoding units according to depths by using Rate-Distortion Optimizationbased on Lagrangian multipliers.

The output unit 130 outputs the image data of the maximum coding unit,which is encoded based on the at least one coded depth determined by thecoding unit determiner 120, and information about the encoding modeaccording to the coded depth, in bitstreams.

The encoded image data may be obtained by encoding residual data of animage.

The information about the encoding mode according to coded depth mayinclude information about the coded depth, about the partition type inthe prediction unit, the prediction mode, and the size of thetransformation unit.

The information about the coded depth may be defined by using splitinformation according to depths, which indicates whether encoding isperformed on coding units of a lower depth instead of a current depth.If the current depth of the current coding unit is the coded depth,image data in the current coding unit is encoded and output, and thusthe split information may be defined not to split the current codingunit to a lower depth. Alternatively, if the current depth of thecurrent coding unit is not the coded depth, the encoding is performed onthe coding unit of the lower depth, and thus the split information maybe defined to split the current coding unit to obtain the coding unitsof the lower depth.

If the current depth is not the coded depth, encoding is performed onthe coding unit that is split into the coding unit of the lower depth.Since at least one coding unit of the lower depth exists in one codingunit of the current depth, the encoding is repeatedly performed on eachcoding unit of the lower depth, and thus the encoding may be recursivelyperformed for the coding units having the same depth.

Since the coding units having a tree structure are determined for onemaximum coding unit, and information about at least one encoding mode isdetermined for a coding unit of a coded depth, information about atleast one encoding mode may be determined for one maximum coding unit.Also, a coded depth of the image data of the maximum coding unit may bedifferent according to locations since the image data is hierarchicallysplit according to depths, and thus information about the coded depthand the encoding mode may be set for the image data.

Accordingly, the output unit 130 may assign encoding information about acorresponding coded depth and an encoding mode to at least one of thecoding unit, the prediction unit, and a minimum unit included in themaximum coding unit.

The minimum unit according to an exemplary embodiment is a rectangulardata unit obtained by splitting the minimum coding unit constituting thelowermost depth by 4. Alternatively, the minimum unit may be a maximumrectangular data unit that may be included in all of the coding units,prediction units, partition units, and transformation units included inthe maximum coding unit.

For example, the encoding information output through the output unit 130may be classified into encoding information according to coding units,and encoding information according to prediction units. The encodinginformation according to the coding units may include the informationabout the prediction mode and about the size of the partitions. Theencoding information according to the prediction units may includeinformation about an estimated direction of an inter mode, about areference image index of the inter mode, about a motion vector, about achroma component of an intra mode, and about an interpolation method ofthe intra mode. Also, information about a maximum size of the codingunit defined according to pictures, slices, or GOPs, and informationabout a maximum depth may be inserted into SPS (Sequence Parameter Set)or a header of a bitstream.

In the video encoding apparatus 100, the deeper coding unit may be acoding unit obtained by dividing a height or width of a coding unit ofan upper depth, which is one layer above, by two. In other words, whenthe size of the coding unit of the current depth is 2N×2N, the size ofthe coding unit of the lower depth is N×N. Also, the coding unit of thecurrent depth having the size of 2N×2N may include a maximum of 4 codingunits of the lower depth.

Accordingly, the video encoding apparatus 100 may form the coding unitshaving the tree structure by determining coding units having an optimumshape and an optimum size for each maximum coding unit, based on thesize of the maximum coding unit and the maximum depth determinedconsidering characteristics of the current picture. Also, since encodingmay be performed on each maximum coding unit by using any one of variousprediction modes and transformations, an optimum encoding mode may bedetermined considering characteristics of the coding unit of variousimage sizes.

Thus, if an image having high resolution or large data amount is encodedin a conventional macroblock, a number of macroblocks per pictureexcessively increases. Accordingly, a number of pieces of compressedinformation generated for each macroblock increases, and thus it isdifficult to transmit the compressed information and data compressionefficiency decreases. However, by using the video encoding apparatus100, image compression efficiency may be increased since a coding unitis adjusted while considering characteristics of an image whileincreasing a maximum size of a coding unit while considering a size ofthe image.

FIG. 2 is a block diagram of a video decoding apparatus 200, accordingto an exemplary embodiment. The video decoding apparatus 200 includes areceiver 210, an image data and encoding information extractor 220, andan image data decoder 230. Definitions of various terms, such as acoding unit, a depth, a prediction unit, a transformation unit, andinformation about various encoding modes, for various operations of thevideo decoding apparatus 200 are identical to those described withreference to FIG. 1 and the video encoding apparatus 100.

The receiver 210 receives and parses a bitstream of an encoded video.The image data and encoding information extractor 220 extracts encodedimage data for each coding unit from the parsed bitstream, wherein thecoding units have a tree structure according to each maximum codingunit, and outputs the extracted image data to the image data decoder230. The image data and encoding information extractor 220 may extractinformation about a maximum size of a coding unit of a current picture,from a header about the current picture or SPS.

Also, the image data and encoding information extractor 220 extractsinformation about a coded depth and an encoding mode for the codingunits having a tree structure according to each maximum coding unit,from the parsed bitstream. The extracted information about the codeddepth and the encoding mode is output to the image data decoder 230. Inother words, the image data in a bit stream is split into the maximumcoding unit so that the image data decoder 230 decodes the image datafor each maximum coding unit.

The information about the coded depth and the encoding mode according tothe maximum coding unit may be set for information about at least onecoding unit corresponding to the coded depth, and information about anencoding mode may include information about a partition type of acorresponding coding unit corresponding to the coded depth, about aprediction mode, and a size of a transformation unit. Also, splittinginformation according to depths may be extracted as the informationabout the coded depth.

The information about the coded depth and the encoding mode according toeach maximum coding unit extracted by the image data and encodinginformation extractor 220 is information about a coded depth and anencoding mode determined to generate a minimum encoding error when anencoder, such as the video encoding apparatus 100, repeatedly performsencoding for each deeper coding unit according to depths according toeach maximum coding unit. Accordingly, the video decoding apparatus 200may restore an image by decoding the image data according to a codeddepth and an encoding mode that generates the minimum encoding error.

Since encoding information about the coded depth and the encoding modemay be assigned to a predetermined data unit from among a correspondingcoding unit, a prediction unit, and a minimum unit, the image data andencoding information extractor 220 may extract the information about thecoded depth and the encoding mode according to the predetermined dataunits. The predetermined data units to which the same information aboutthe coded depth and the encoding mode is assigned may be inferred to bethe data units included in the same maximum coding unit.

The image data decoder 230 restores the current picture by decoding theimage data in each maximum coding unit based on the information aboutthe coded depth and the encoding mode according to the maximum codingunits. In other words, the image data decoder 230 may decode the encodedimage data based on the extracted information about the partition type,the prediction mode, and the transformation unit for each coding unitfrom among the coding units having the tree structure included in eachmaximum coding unit. A decoding process may include a predictionincluding intra prediction and motion compensation, and an inversetransformation. Inverse transformation may be performed according tomethod of inverse orthogonal transformation or inverse integertransformation.

The image data decoder 230 may perform intra prediction or motioncompensation according to a partition and a prediction mode of eachcoding unit, based on the information about the partition type and theprediction mode of the prediction unit of the coding unit according tocoded depths.

Also, the image data decoder 230 may perform inverse transformationaccording to each transformation unit in the coding unit, based on theinformation about the size of the transformation unit of the coding unitaccording to coded depths, so as to perform the inverse transformationaccording to maximum coding units.

The image data decoder 230 may determine at least one coded depth of acurrent maximum coding unit by using split information according todepths. If the split information indicates that image data is no longersplit in the current depth, the current depth is a coded depth.Accordingly, the image data decoder 230 may decode encoded data of atleast one coding unit corresponding to the each coded depth in thecurrent maximum coding unit by using the information about the partitiontype of the prediction unit, the prediction mode, and the size of thetransformation unit for each coding unit corresponding to the codeddepth, and output the image data of the current maximum coding unit.

In other words, data units containing the encoding information includingthe same split information may be gathered by observing the encodinginformation set assigned for the predetermined data unit from among thecoding unit, the prediction unit, and the minimum unit, and the gathereddata units may be considered to be one data unit to be decoded by theimage data decoder 230 in the same encoding mode.

The video decoding apparatus 200 may obtain information about at leastone coding unit that generates the minimum encoding error when encodingis recursively performed for each maximum coding unit, and may use theinformation to decode the current picture. In other words, the codingunits having the tree structure determined to be the optimum codingunits in each maximum coding unit may be decoded. Also, the maximum sizeof coding unit is determined considering resolution and an amount ofimage data.

Accordingly, even if image data has high resolution and a large amountof data, the image data may be efficiently decoded and restored by usinga size of a coding unit and an encoding mode, which are adaptivelydetermined according to characteristics of the image data, by usinginformation about an optimum encoding mode received from an encoder.

A method of determining coding units having a tree structure, aprediction unit, and a transformation unit, according to an exemplaryembodiment, will now be described with reference to FIGS. 3 through 13.

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment.

A size of a coding unit may be expressed in width×height, and may be64×64, 32×32, 16×16, and 8×8. A coding unit of 64×64 may be split intopartitions of 64×64, 64×32, 32×64, or 32×32, and a coding unit of 32×32may be split into partitions of 32×32, 32×16, 16×32, or 16×16, a codingunit of 16×16 may be split into partitions of 16×16, 16×8, 8×16, or 8×8,and a coding unit of 8×8 may be split into partitions of 8×8, 8×4, 4×8,or 4×4.

In video data 310, a resolution is 1920×1080, a maximum size of a codingunit is 64, and a maximum depth is 2. In video data 320, a resolution is1920×1080, a maximum size of a coding unit is 64, and a maximum depth is3. In video data 330, a resolution is 352×288, a maximum size of acoding unit is 16, and a maximum depth is 1. The maximum depth shown inFIG. 3 denotes a total number of splits from a maximum coding unit to aminimum decoding unit.

If a resolution is high or a data amount is large, a maximum size of acoding unit may be large so as to not only increase encoding efficiencybut also to accurately reflect characteristics of an image. Accordingly,the maximum size of the coding unit of the video data 310 and 320 havingthe higher resolution than the video data 330 may be 64.

Since the maximum depth of the video data 310 is 2, coding units 315 ofthe vide data 310 may include a maximum coding unit having a long axissize of 64, and coding units having long axis sizes of 32 and 16 sincedepths are deepened to two layers by splitting the maximum coding unittwice. Meanwhile, since the maximum depth of the video data 330 is 1,coding units 335 of the video data 330 may include a maximum coding unithaving a long axis size of 16, and coding units having a long axis sizeof 8 since depths are deepened to one layer by splitting the maximumcoding unit once.

Since the maximum depth of the video data 320 is 3, coding units 325 ofthe video data 320 may include a maximum coding unit having a long axissize of 64, and coding units having long axis sizes of 32, 16, and 8since the depths are deepened to 3 layers by splitting the maximumcoding unit three times. As a depth deepens, detailed information may beprecisely expressed.

FIG. 4 is a block diagram of an image encoder 400 based on coding units,according to an exemplary embodiment. The image encoder 400 performsoperations of the coding unit determiner 120 of the video encodingapparatus 100 to encode image data. In other words, an intra predictor410 performs intra prediction on coding units in an intra mode, fromamong a current frame 405, and a motion estimator 420 and a motioncompensator 425 performs inter estimation and motion compensation oncoding units in an inter mode from among the current frame 405 by usingthe current frame 405, and a reference frame 495.

Data output from the intra predictor 410, the motion estimator 420, andthe motion compensator 425 is output as a quantized transformationcoefficient through a transformer 430 and a quantizer 440. The quantizedtransformation coefficient is restored as data in a spatial domainthrough an inverse quantizer 460 and an inverse transformer 470, and therestored data in the spatial domain is output as the reference frame 495after being post-processed through a deblocking unit 480 and a loopfiltering unit 490. The quantized transformation coefficient may beoutput as a bitstream 455 through an entropy encoder 450.

In order for the image encoder 400 to be applied in the video encodingapparatus 100, all elements of the image encoder 400, i.e., the intrapredictor 410, the motion estimator 420, the motion compensator 425, thetransformer 430, the quantizer 440, the entropy encoder 450, the inversequantizer 460, the inverse transformer 470, the deblocking unit 480, andthe loop filtering unit 490 perform operations based on each coding unitfrom among coding units having a tree structure while considering themaximum depth of each maximum coding unit.

Specifically, the intra predictor 410, the motion estimator 420, and themotion compensator 425 determines partitions and a prediction mode ofeach coding unit from among the coding units having a tree structurewhile considering the maximum size and the maximum depth of a currentmaximum coding unit, and the transformer 430 determines the size of thetransformation unit in each coding unit from among the coding unitshaving a tree structure.

FIG. 5 is a block diagram of an image decoder 500 based on coding units,according to an exemplary embodiment. A parser 510 parses encoded imagedata to be decoded and information about encoding required for decodingfrom a bitstream 505. The encoded image data is output as inversequantized data through an entropy decoder 520 and an inverse quantizer530, and the inverse quantized data is restored to image data in aspatial domain through an inverse transformer 540.

An intra predictor 550 performs intra prediction on coding units in anintra mode with respect to the image data in the spatial domain, and amotion compensator 560 performs motion compensation on coding units inan inter mode by using a reference frame 585.

The image data in the spatial domain, which passed through the intrapredictor 550 and the motion compensator 560, may be output as arestored frame 595 after being post-processed through a deblocking unit570 and a loop filtering unit 580. Also, the image data that ispost-processed through the deblocking unit 570 and the loop filteringunit 580 may be output as the reference frame 585.

In order to decode the image data in the image data decoder 230 of thevideo decoding apparatus 200, the image decoder 500 may performoperations that are performed after the parser 510.

In order for the image decoder 500 to be applied in the video decodingapparatus 200, all elements of the image decoder 500, i.e., the parser510, the entropy decoder 520, the inverse quantizer 530, the inversetransformer 540, the intra predictor 550, the motion compensator 560,the deblocking unit 570, and the loop filtering unit 580 performoperations based on coding units having a tree structure for eachmaximum coding unit.

Specifically, the intra predictor 550 and the motion compensator 560perform operations based on partitions and a prediction mode for each ofthe coding units having a tree structure, and the inverse transformer540 perform operations based on a size of a transformation unit for eachcoding unit.

FIG. 6 is a diagram illustrating deeper coding units according todepths, and partitions, according to an exemplary embodiment. The videoencoding apparatus 100 and the video decoding apparatus 200 usehierarchical coding units so as to consider characteristics of an image.A maximum height, a maximum width, and a maximum depth of coding unitsmay be adaptively determined according to the characteristics of theimage, or may be differently set by a user. Sizes of deeper coding unitsaccording to depths may be determined according to the predeterminedmaximum size of the coding unit.

In a hierarchical structure 600 of coding units, according to anexemplary embodiment, the maximum height and the maximum width of thecoding units are each 64, and the maximum depth is 4. Since a depthdeepens along a vertical axis of the hierarchical structure 600, aheight and a width of the deeper coding unit are each split. Also, aprediction unit and partitions, which are bases for prediction encodingof each deeper coding unit, are shown along a horizontal axis of thehierarchical structure 600.

In other words, a coding unit 610 is a maximum coding unit in thehierarchical structure 600, wherein a depth is 0 and a size, i.e., aheight by width, is 64×64. The depth deepens along the vertical axis,and a coding unit 620 having a size of 32×32 and a depth of 1, a codingunit 630 having a size of 16×16 and a depth of 2, a coding unit 640having a size of 8×8 and a depth of 3, and a coding unit 650 having asize of 4×4 and a depth of 4 exist. The coding unit 650 having the sizeof 4×4 and the depth of 4 is a minimum coding unit.

The prediction unit and the partitions of a coding unit are arrangedalong the horizontal axis according to each depth. In other words, ifthe coding unit 610 having the size of 64×64 and the depth of 0 is aprediction unit, the prediction unit may be split into partitionsinclude in the encoding unit 610, i.e. a partition 610 having a size of64×64, partitions 612 having the size of 64×32, partitions 614 havingthe size of 32×64, or partitions 616 having the size of 32×32.

Similarly, a prediction unit of the coding unit 620 having the size of32×32 and the depth of 1 may be split into partitions included in thecoding unit 620, i.e. a partition 620 having a size of 32×32, partitions622 having a size of 32×16, partitions 624 having a size of 16×32, andpartitions 626 having a size of 16×16.

Similarly, a prediction unit of the coding unit 630 having the size of16×16 and the depth of 2 may be split into partitions included in thecoding unit 630, i.e. a partition having a size of 16×16 included in thecoding unit 630, partitions 632 having a size of 16×8, partitions 634having a size of 8×16, and partitions 636 having a size of 8×8.

Similarly, a prediction unit of the coding unit 640 having the size of8×8 and the depth of 3 may be split into partitions included in thecoding unit 640, i.e. a partition having a size of 8×8 included in thecoding unit 640, partitions 642 having a size of 8×4, partitions 644having a size of 4×8, and partitions 646 having a size of 4×4.

The coding unit 650 having the size of 4×4 and the depth of 4 is theminimum coding unit and a coding unit of the lowermost depth. Aprediction unit of the coding unit 650 is only assigned to a partitionhaving a size of 4×4.

In order to determine the at least one coded depth of the coding unitsconstituting the maximum coding unit 610, the coding unit determiner 120of the video encoding apparatus 100 performs encoding for coding unitscorresponding to each depth included in the maximum coding unit 610.

A number of deeper coding units according to depths including data inthe same range and the same size increases as the depth deepens. Forexample, four coding units corresponding to a depth of 2 are required tocover data that is included in one coding unit corresponding to a depthof 1. Accordingly, in order to compare encoding results of the same dataaccording to depths, the coding unit corresponding to the depth of 1 andfour coding units corresponding to the depth of 2 are each encoded.

In order to perform encoding for a current depth from among the depths,a least encoding error may be selected for the current depth byperforming encoding for each prediction unit in the coding unitscorresponding to the current depth, along the horizontal axis of thehierarchical structure 600. Alternatively, the minimum encoding errormay be searched for by comparing the least encoding errors according todepths, by performing encoding for each depth as the depth deepens alongthe vertical axis of the hierarchical structure 600. A depth and apartition having the minimum encoding error in the coding unit 610 maybe selected as the coded depth and a partition type of the coding unit610.

FIG. 7 is a diagram for describing a relationship between a coding unit710 and transformation units 720, according to an exemplary embodiment.The video encoding apparatus 100 or 200 encodes or decodes an imageaccording to coding units having sizes smaller than or equal to amaximum coding unit for each maximum coding unit. Sizes oftransformation units for transformation during encoding may be selectedbased on data units that are not larger than a corresponding codingunit.

For example, in the video encoding apparatus 100 or 200, if a size ofthe coding unit 710 is 64×64, transformation may be performed by usingthe transformation units 720 having a size of 32×32.

Also, data of the coding unit 710 having the size of 64×64 may beencoded by performing the transformation on each of the transformationunits having the size of 32×32, 16×16, 8×8, and 4×4, which are smallerthan 64×64, and then a transformation unit having the least coding errormay be selected.

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment.The output unit 130 of the video encoding apparatus 100 may encode andtransmit information 800 about a partition type, information 810 about aprediction mode, and information 820 about a size of a transformationunit for each coding unit corresponding to a coded depth, as informationabout an encoding mode.

The information 800 indicates information about a shape of a partitionobtained by splitting a prediction unit of a current coding unit,wherein the partition is a data unit for prediction encoding the currentcoding unit. For example, a current coding unit CU_(—)0 having a size of2N×2N may be split into any one of a partition 802 having a size of2N×2N, a partition 804 having a size of 2N×N, a partition 806 having asize of N×2N, and a partition 808 having a size of N×N. Here, theinformation 800 about a partition type is set to indicate one of thepartition 804 having a size of 2N×N, the partition 806 having a size ofN×2N, and the partition 808 having a size of N×N

The information 810 indicates a prediction mode of each partition. Forexample, the information 810 may indicate a mode of prediction encodingperformed on a partition indicated by the information 800, i.e., anintra mode 812, an inter mode 814, or a skip mode 816.

The information 820 indicates a transformation unit to be based on whentransformation is performed on a current coding unit. For example, thetransformation unit may be a first intra transformation unit 822, asecond intra transformation unit 824, a first inter transformation unit826, or a second intra transformation unit 828.

The image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract and use the information 800, 810, and820 for decoding, according to each deeper coding unit

FIG. 9 is a diagram of deeper coding units according to depths,according to an exemplary embodiment. Split information may be used toindicate a change of a depth. The spilt information indicates whether acoding unit of a current depth is split into coding units of a lowerdepth.

A prediction unit 910 for prediction encoding a coding unit 900 having adepth of 0 and a size of 2N_(—)0×2N_(—)0 may include partitions of apartition type 912 having a size of 2N_(—)0×2N_(—)0, a partition type914 having a size of 2N_(—)0×N_(—)0, a partition type 916 having a sizeof N_(—)0×2N_(—)0, and a partition type 918 having a size ofN_(—)0×N_(—)0. FIG. 9 only illustrates the partition types 912 through918 which are obtained by symmetrically splitting the prediction unit910, but a partition type is not limited thereto, and the partitions ofthe prediction unit 910 may include asymmetrical partitions, partitionshaving a predetermined shape, and partitions having a geometrical shape.

Prediction encoding is repeatedly performed on one partition having asize of 2N_(—)0×2N_(—)0, two partitions having a size of 2N_(—)0×N_(—)0,two partitions having a size of N_(—)0×2N_(—)0, and four partitionshaving a size of N_(—)0×N_(—)0, according to each partition type. Theprediction encoding in an intra mode and an inter mode may be performedon the partitions having the sizes of 2N_(—)0×2N_(—)0, N_(—)0×2N_(—)0,2N_(—)0×N_(—)0, and N_(—)0×N_(—)0. The prediction encoding in a skipmode is performed only on the partition having the size of2N_(—)0×2N_(—)0.

Errors of encoding including the prediction encoding in the partitiontypes 912 through 918 are compared, and the least encoding error isdetermined among the partition types. If an encoding error is smallestin one of the partition types 912 through 916, the prediction unit 910may not be split into a lower depth.

If the encoding error is the smallest in the partition type 918, a depthis changed from 0 to 1 to split the partition type 918 in operation 920,and encoding is repeatedly performed on coding units 930 having a depthof 2 and a size of N_(—)0×N_(—)0 to search for a minimum encoding error.

A prediction unit 940 for prediction encoding the coding unit 930 havinga depth of 1 and a size of 2N_(—)1×2N_(—)1 (=N_(—)0×N_(—)0) may includepartitions of a partition type 942 having a size of 2N_(—)1×2N_(—)1, apartition type 944 having a size of 2N_(—)1×N_(—)1, a partition type 946having a size of N_(—)1×2N_(—)1, and a partition type 948 having a sizeof N_(—)1×N_(—)1.

If an encoding error is the smallest in the partition type 948, a depthis changed from 1 to 2 to split the partition type 948 in operation 950,and encoding is repeatedly performed on coding units 960, which have adepth of 2 and a size of N_(—)2×N_(—)2 to search for a minimum encodingerror.

When a maximum depth is d, split operation according to each depth maybe performed up to when a depth becomes d−1, and split information maybe encoded as up to when a depth is one of 0 to d−2. In other words,when encoding is performed up to when the depth is d−1 after a codingunit corresponding to a depth of d−2 is split in operation 970, aprediction unit 990 for prediction encoding a coding unit 980 having adepth of d−1 and a size of 2N_(d−1)×2N_(d−1) may include partitions of apartition type 992 having a size of 2N_(d−1)×2N_(d−1), a partition type994 having a size of 2N_(d−1)×N_(d−1), a partition type 996 having asize of N_(d−1)×2N_(d−1), and a partition type 998 having a size ofN_(d−1)×N_(d−1).

Prediction encoding may be repeatedly performed on one partition havinga size of 2N_(d−1)×2N_(d−1), two partitions having a size of2N_(d−1)×N_(d−1), two partitions having a size of N_(d−1)×2N_(d−1), fourpartitions having a size of N_(d−1)×N_(d−1) from among the partitiontypes 992 through 998 to search for a partition type having a minimumencoding error.

Even when the partition type 998 has the minimum encoding error, since amaximum depth is d, a coding unit CU_(d−1) having a depth of d−1 is nolonger split to a lower depth, and a coded depth for the coding unitsconstituting a current maximum coding unit 900 is determined to be d−1and a partition type of the current maximum coding unit 900 may bedetermined to be N_(d−1)×N_(d−1). Also, since the maximum depth is d anda minimum coding unit 980 having a lowermost depth of d−1 is no longersplit to a lower depth, split information for the minimum coding unit980 is not set.

A data unit 999 may be a ‘minimum unit’ for the current maximum codingunit. A minimum unit according to an exemplary embodiment may be arectangular data unit obtained by splitting a minimum coding unit 980 by4. By performing the encoding repeatedly, the video encoding apparatus100 may select a depth having the least encoding error by comparingencoding errors according to depths of the coding unit 900 to determinea coded depth, and set a corresponding partition type and a predictionmode as an encoding mode of the coded depth.

As such, the minimum encoding errors according to depths are compared inall of the depths of 1 through d, and a depth having the least encodingerror may be determined as a coded depth. The coded depth, the partitiontype of the prediction unit, and the prediction mode may be encoded andtransmitted as information about an encoding mode. Also, since a codingunit is split from a depth of 0 to a coded depth, only split informationof the coded depth is set to 0, and split information of depthsexcluding the coded depth is set to 1.

The image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract and use the information about thecoded depth and the prediction unit of the coding unit 900 to decode thepartition 912. The video decoding apparatus 200 may determine a depth,in which split information is 0, as a coded depth by using splitinformation according to depths, and use information about an encodingmode of the corresponding depth for decoding.

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units 1010, prediction units 1060, and transformation units 1070,according to an exemplary embodiment. The coding units 1010 are codingunits having a tree structure, corresponding to coded depths determinedby the video encoding apparatus 100, in a maximum coding unit. Theprediction units 1060 are partitions of prediction units of each of thecoding units 1010, and the transformation units 1070 are transformationunits of each of the coding units 1010.

When a depth of a maximum coding unit is 0 in the coding units 1010,depths of coding units 1012 and 1054 are 1, depths of coding units 1014,1016, 1018, 1028, 1050, and 1052 are 2, depths of coding units 1020,1022, 1024, 1026, 1030, 1032, and 1048 are 3, and depths of coding units1040, 1042, 1044, and 1046 are 4.

In the prediction units 1060, some encoding units 1014, 1016, 1022,1032, 1048, 1050, 1052, and 1054 are obtained by splitting the codingunits in the encoding units 1010. In other words, partition types in thecoding units 1014, 1022, 1050, and 1054 have a size of 2N×N, partitiontypes in the coding units 1016, 1048, and 1052 have a size of N×2N, anda partition type of the coding unit 1032 has a size of N×N. Predictionunits and partitions of the coding units 1010 are smaller than or equalto each coding unit.

Transformation or inverse transformation is performed on image data ofthe coding unit 1052 in the transformation units 1070 in a data unitthat is smaller than the coding unit 1052. Also, the coding units 1014,1016, 1022, 1032, 1048, 1050, and 1052 in the transformation units 1070are different from those in the prediction units 1060 in terms of sizesand shapes. In other words, the video encoding and decoding apparatuses100 and 200 may perform intra prediction, motion estimation, motioncompensation, transformation, and inverse transformation individually ona data unit in the same coding unit.

Accordingly, encoding is recursively performed on each of coding unitshaving a hierarchical structure in each region of a maximum coding unitto determine an optimum coding unit, and thus coding units having arecursive tree structure may be obtained. Encoding information mayinclude split information about a coding unit, information about apartition type, information about a prediction mode, and informationabout a size of a transformation unit. Table 1 shows the encodinginformation that may be set by the video encoding and decodingapparatuses 100 and 200.

TABLE 1 Split Information 0 (Encoding on Coding Unit Having Size of 2N ×2N and Current Depth of d) Partition Type Size of Transformation UnitSymmetrical Asymmetrical Split Information 0 Split Information 1Prediction Partition Partition of Transformation of Transformation SplitMode Type Type Unit Unit Information 1 Intra 2N × 2N 2N × nU 2N × 2N N ×N Repeatedly Encode Inter 2N × N 2N × nD (Symmetrical Type) Coding UnitsSkip (Only  N × 2N nL × 2N N/2 × N/2 Having Lower 2N × 2N)  N × N nR ×2N (Asymmetrical Type) Depth of d + 1

The output unit 130 of the video encoding apparatus 100 may output theencoding information about the coding units having a tree structure, andthe image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract the encoding information about thecoding units having a tree structure from a received bitstream.

Split information indicates whether a current coding unit is split intocoding units of a lower depth. If split information of a current depth dis 0, a depth, in which a current coding unit is no longer split into alower depth, is a coded depth, and thus information about a partitiontype, prediction mode, and a size of a transformation unit may bedefined for the coded depth. If the current coding unit is further splitaccording to the split information, encoding is independently performedon four split coding units of a lower depth.

A prediction mode may be one of an intra mode, an inter mode, and a skipmode. The intra mode and the inter mode may be defined in all partitiontypes, and the skip mode is defined only in a partition type having asize of 2N×2N.

The information about the partition type may indicate symmetricalpartition types having sizes of 2N×2N, 2N×N, N×2N, and N×N, which areobtained by symmetrically splitting a height or a width of a predictionunit, and asymmetrical partition types having sizes of 2N×nU, 2N×nD,nL×2N, and nR×2N, which are obtained by asymmetrically splitting theheight or width of the prediction unit. The asymmetrical partition typeshaving the sizes of 2N×nU and 2N×nD may be respectively obtained bysplitting the height of the prediction unit in 1:3 and 3:1, and theasymmetrical partition types having the sizes of nL×2N and nR×2N may berespectively obtained by splitting the width of the prediction unit in1:3 and 3:1

The size of the transformation unit may be set to be two types in theintra mode and two types in the inter mode. In other words, if splitinformation of the transformation unit is 0, the size of thetransformation unit may be 2N×2N, which is the size of the currentcoding unit. If split information of the transformation unit is 1, thetransformation units may be obtained by splitting the current codingunit. Also, if a partition type of the current coding unit having thesize of 2N×2N is a symmetrical partition type, a size of atransformation unit may be N×N, and if the partition type of the currentcoding unit is an asymmetrical partition type, the size of thetransformation unit may be N/2×N/2.

The encoding information about coding units having a tree structure mayinclude at least one of a coding unit corresponding to a coded depth, aprediction unit, and a minimum unit. The coding unit corresponding tothe coded depth may include at least one of a prediction unit and aminimum unit containing the same encoding information.

Accordingly, it is determined whether adjacent data units are includedin the same coding unit corresponding to the coded depth by comparingencoding information of the adjacent data units. Also, a correspondingcoding unit corresponding to a coded depth is determined by usingencoding information of a data unit, and thus a distribution of codeddepths in a maximum coding unit may be determined.

Accordingly, if a current coding unit is predicted based on encodinginformation of adjacent data units, encoding information of data unitsin deeper coding units adjacent to the current coding unit may bedirectly referred to and used.

Alternatively, if a current coding unit is predicted based on encodinginformation of adjacent data units, data units adjacent to the currentcoding unit are searched using encoded information of the data units,and the searched adjacent coding units may be referred for predictingthe current coding unit.

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information of Table 1. A maximum coding unit1300 includes coding units 1302, 1304, 1306, 1312, 1314, 1316, and 1318of coded depths. Here, since the coding unit 1318 is a coding unit of acoded depth, split information may be set to 0. Information about apartition type of the coding unit 1318 having a size of 2N×2N may be setto be one of a partition type 1322 having a size of 2N×2N, a partitiontype 1324 having a size of 2N×N, a partition type 1326 having a size ofN×2N, a partition type 1328 having a size of N×N, a partition type 1332having a size of 2N×nU, a partition type 1334 having a size of 2N×nD, apartition type 1336 having a size of nL×2N, and a partition type 1338having a size of nR×2N.

When the partition type is set to be symmetrical, i.e. the partitiontype 1322, 1324, 1326, or 1328, a transformation unit 1342 having a sizeof 2N×2N is set if split information (TU size flag) of a transformationunit is 0, and a transformation unit 1344 having a size of N×N is set ifa TU size flag is 1.

When the partition type is set to be asymmetrical, i.e., the partitiontype 1332, 1334, 1336, or 1338, a transformation unit 1352 having a sizeof 2N×2N is set if a TU size flag is 0, and a transformation unit 1354having a size of N/2×N/2 is set if a TU size flag is 1.

Referring to FIG. 13, the TU size flag is a flag having a value or 0 or1, but the TU size flag is not limited to 1 bit, and a transformationunit may be hierarchically split having a tree structure while the TUsize flag increases from 0.

FIG. 14 is a flowchart illustrating a method of encoding a video,according to an embodiment. In operation 1210, a current picture issplit into at least one maximum coding unit. A maximum depth indicatingthe total number of possible splitting times may be predetermined.

In operation 1220, a coded depth to output a final encoding resultaccording to at least one split region, which is obtained by splitting aregion of each maximum coding unit according to depths, is determined byencoding the at least one split region, and a coding unit according to atree structure is determined.

The maximum coding unit is spatially split whenever the depth deepens,and thus is split into coding units of a lower depth. Each coding unitmay be split into coding units of another lower depth by being spatiallysplit independently from adjacent coding units. Encoding is repeatedlyperformed on each coding unit according to depths.

Also, a transformation unit according to partition types having theleast encoding error is determined for each deeper coding unit. In orderto determine a coded depth having a minimum encoding error in eachmaximum coding unit, encoding errors may be measured and compared in alldeeper coding units according to depths.

In operation 1230, encoded image data constituting the final encodingresult according to the coded depth is output for each maximum codingunit, with encoding information about the coded depth and an encodingmode. The information about the encoding mode may include informationabout a coded depth or split information, information about a partitiontype of a prediction unit, a prediction mode, and a size of atransformation unit. The encoded information about the encoding mode maybe transmitted to a decoder with the encoded image data.

FIG. 15 is a flowchart illustrating a method of decoding a video,according to an exemplary embodiment. In operation 1310, a bitstream ofan encoded video is received and parsed.

In operation 1320, encoded image data of a current picture assigned to amaximum coding unit, and information about a coded depth and an encodingmode according to maximum coding units are extracted from the parsedbitstream. The coded depth of each maximum coding unit is a depth havingthe least encoding error in each maximum coding unit. In encoding eachmaximum coding unit, the image data is encoded based on at least onedata unit obtained by hierarchically splitting the each maximum codingunit according to depths.

According to the information about the coded depth and the encodingmode, the maximum coding unit may be split into coding units having atree structure. Each of the coding units having the tree structure isdetermined as a coding unit corresponding to a coded depth, and isoptimally encoded as to output the least encoding error. Accordingly,encoding and decoding efficiency of an image may be improved by decodingeach piece of encoded image data in the coding units after determiningat least one coded depth according to coding units.

In operation 1330, the image data of each maximum coding unit is decodedbased on the information about the coded depth and the encoding modeaccording to the maximum coding units. The decoded image data may bereproduced by a reproducing apparatus, stored in a storage medium, ortransmitted through a network.

Hereinafter, encoding and decoding video by performing deblockingfiltering in consideration of coding units, prediction units, andtransformation units, according to exemplary embodiments, will bedescribed with reference to FIGS. 16 through 24.

FIG. 16 is a block diagram of a video encoding apparatus 1400 employingdeblocking filtering, according to an exemplary embodiment. Referring toFIG. 16, the video encoding apparatus 1400 includes a maximum codingunit splitter 1410, a coding unit and encoding mode determiner 1420, anda deblocking filtering performing unit 1430.

The video encoding apparatus 1400 is another exemplary embodiment of thevideo encoding apparatus 100. Specifically, the maximum coding unitsplitter 1410 may correspond to the maximum coding unit splitter 110included in the video encoding apparatus 100, and the coding unit andencoding mode determiner 1420 and the deblocking filtering performingunit 1430 may correspond to the coding unit determiner 120 included inthe video encoding apparatus 100.

The maximum coding unit splitter 1410 may split a picture of input videodata into maximum coding units, and output a result of the splitting tothe coding unit and encoding mode determiner 1420.

The coding unit and encoding mode determiner 1420 may individuallydetermine coding units corresponding to depths and encoding modes havingthe least encoding error with respect to each region of each of themaximum coding units by repeatedly performing prediction encoding andtransformation on the maximum coding units in coding units according todepths. Here, prediction encoding may be performed in variouspartition-type prediction units and transformation may be performed invarious-sized transformation units.

The encoding mode for each of the coding units may contain informationregarding a partition type of the coding unit, which represents the sizeand shape of a prediction unit, a prediction mode, e.g., an inter mode,an intra mode, or a skip mode, and the size of transformation unit usedwhen performing encoding that causes the least encoding error.

According to an exemplary embodiment, the partition type of the codingunit may include not only symmetrical partition types having sizes ofN×N, N×2N, 2N×N, and 2N×2N but also asymmetrical partition typesobtained by splitting the height or width of the coding unit in 1:3 or3:1. According to an exemplary embodiment, the size of thetransformation unit may be 2×2, 4×4, 8×8, 16×16, 32×32, 64×64, or128×128,

The deblocking filtering performing unit 1430 may receive video databeing inversely transformed into a spatial domain, and performdeblocking filtering on the video data in the spatial domain inconsideration of the encoding modes of the coding units of the videodata. Specifically, quantized transformation coefficients, which wereobtained by the coding unit and encoding mode determiner 1420 predictionencoding the coding units on the basis of prediction units, transforminga result of the encoding on the basis of transformation units, andquantizing a final result in the coding units based on the coded depth,may be inversely quantized and inversely transformed back into the videodata in the spatial domain, and transmitted to the deblocking filteringperforming unit 1430.

The deblocking filtering performing unit 1430 may perform deblockingfiltering on boundaries of the prediction units or the transformationunits in the coding units of the video data in the spatial domain, inconsideration of the encoding modes of the coding units.

Deblocking filtering may be recursively and repeatedly performed on thecoding units of each of the maximum coding units. For example, if splitinformation of a coding unit is ‘1’, then a current depth is not a codeddepth. Thus, deblocking filtering is not performed and the coding unitof the current depth may be further divided into coding units of lowerdepths. If the split information of the coding unit is ‘0’, then thecurrent depth is a coded depth. Thus, deblocking filtering is performedon left, upper, and internal boundaries of the coding unit correspondingto the current depth.

The deblocking filtering performing unit 1430 may perform deblockingfiltering by considering whether current boundaries correspond toboundaries of at least one from among a coding unit, a prediction unit,and a transformation unit. For example, boundary strength may be setbased on whether current boundaries correspond to boundaries of at leastone from among a coding unit, a prediction unit, and a transformationunit.

The deblocking filtering performing unit 1430 may perform deblockingfiltering by considering at least one from among coding unit size,prediction unit size, and transformation unit size defined in theencoding modes of the coding units. Otherwise, the deblocking filteringperforming unit 1430 may perform deblocking filtering by consideringpartition types of the coding units.

In addition, the deblocking filtering performing unit 1430 may performdeblocking filtering by considering at least one from among a predictionmode of each prediction unit, whether an encoded residual component ispresent, a motion vector, the number of reference pictures, and an indexof a reference picture, defined in the encoding modes of the codingunits.

The deblocking filtering performing unit 1430 may determine boundarystrength in consideration of the encoding modes of the coding units. Thedeblocking filtering performing unit 1430 may determine whetherdeblocking filtering is to be performed or may determine a deblockingfiltering method, in consideration of the encoding modes of the codingunits. Otherwise, the deblocking filtering performing unit 1430 mayperform deblocking filtering, based on the boundary strength, whetherdeblocking filtering is to be performed, and the deblocking filteringmethod that are determined in consideration of the encoding modes of thecoding units.

The deblocking filtering method may include setting of the length of adeblocking filter, filter tab size, and location of a sample that is tobe deblocking filtered. In this case, the sample may include theoriginal value of a pixel, which is a deblocking filtering coefficient,and a pixel, the value of which is changed by performing deblockingfiltering.

For example, an output value of a predetermined linear formula, thevariables of which are filter coefficients, may be determined as adeblocking filtering output value by using a deblocking filter that usesthe original values of pixels perpendicular to a boundary ascoefficients.

The video data that is deblocking filtered in the coding units by thedeblocking filtering performing unit 1430, may be loop filtered to beused as a reference picture for motion estimation and compensation for asubsequent picture.

The video encoding apparatus 1400 employing deblocking filtering mayquantize and entropy encode transformation coefficients in coding units,and may output a bitstream that contains video data encoded in maximumcoding units and information regarding a coded depth and an encodingmode for each of the coding units.

FIG. 17 is a block diagram of a video decoding apparatus 1500 employingdeblocking filtering, according to an exemplary embodiment. Referring toFIG. 17, the video decoding apparatus 1500 includes a data extractor1510, an entropy decoding and inverse quantization unit 1520, an inversetransformation and prediction decoding unit 1530, and a deblockingfiltering performing unit 1540.

The video decoding apparatus 1500 employing deblocking filteringcorresponds to the video decoding apparatus 200 of FIG. 2. Specifically,the data extractor 1510 may correspond to the image data and encodinginformation extractor 220 included in the video decoding apparatus 200,and the entropy decoding and inverse quantization unit 1520, the inversetransformation and prediction decoding unit 1530, and the deblockingfiltering performing unit 1540 may correspond to the image data decoder230 included in the video decoding apparatus 200.

The data extractor 1510 may parse a received bitstream to extract anencode mode of each of coding units and video data encoded in the codingunits. Information regarding the size of a maximum coding unit mayfurther be extracted from the parsing result of the bitstream.

The encoding mode of each of the coding units may contain informationregarding coded depths, prediction units, a prediction mode, andtransformation units that are used to decode the encoded video data.Thus, the encoded video data may be extracted in the coding units fromthe parsing result according to the encoding mode of each of the codingunits.

The entropy decoding and inverse quantization unit 1520 may outputtransformation coefficients by entropy decoding and inversely quantizingthe encoded video data received from the data extractor 1510.Specifically, quantized transformation coefficients may be output byentropy decoding the encoded video data, and transformation coefficientscorresponding to the coding units may be output by inversely quantizingthe quantized transformation coefficients.

The inverse transformation and prediction decoding unit 1530 may outputvideo data in a spatial domain by inversely transforming and predictiondecoding the transformation coefficients corresponding to the codingunits, received from the entropy decoding and inverse quantization unit1520.

Specifically, in the inverse transforming, the transformationcoefficients corresponding to the coding units may be inverselytransformed based on the information regarding transformation units,which is obtained from the encoding modes of the coding units extractedby the data extractor 1510, thereby producing residual data for each ofthe coding units.

In the prediction decoding, the residual data for each of the codingunits may be intra predicted and motion compensated based on theinformation regarding prediction units, which is obtained from theextracted encoding modes of the coding units, thereby reconstructing thevideo data in the spatial domain in the coding units.

The deblocking filtering performing unit 1540 may perform deblockingfiltering on the video data in the spatial domain received from theinverse transformation and prediction decoding unit 1530, inconsideration of the encoding modes of the coding units.

Otherwise, the deblocking filtering performing unit 1540 may performdeblocking filtering on the video data in the spatial domain in maximumcoding units, based on the extracted encoding modes of the coding units.Deblocking filtering may be performed on boundaries of the predictionunits or of the transformation units in the coding units.

The deblocking filtering performing unit 1530 may recursively andrepeatedly perform deblocking filtering on coding units included in eachof the maximum coding units. For example, if split information of acoding unit is ‘1’, a current depth is not a coded depth. Thus,deblocking filtering is not performed for a coding unit of the currentdepth and the coding unit of the current depth may be further dividedinto coding units of lower depths. If the split information of thecoding unit is ‘0’, the current depth is a coded depth. Thus, deblockingfiltering is performed on left, upper, and internal boundaries of thecoding unit corresponding to the current depth.

Similar to as described above, the deblocking filtering 1430 may performdeblocking filtering, depending on whether a current boundary correspondto boundaries of a coding unit, the prediction units, and thetransformation units according to the encoding modes of the codingunits.

Various examples of an encoding mode considered for deblocking filteringmay include coding unit size, prediction size, transformation unit size,and partition types of the coding units, defined in the encoding modesof the coding units. Also, deblocking filtering may be performed inconsideration of at least one from among a prediction mode, whether anencoded residual component exists, a motion vector, the number ofreference pictures, and an index of a reference picture, similar tovideo codec according to the existing standards.

Also, deblocking filtering may be performed in consideration of encodingmodes of coding units, prediction units, and transformation units,according to a deblocking filtering method that includes informationregarding a deblocking filter according to boundary strength determinedbased on the above various examples of encoding modes, whetherdeblocking filtering is to be performed, and filter tab size.

A result of deblocking filtering the video data may be output asreproduced video in the spatial domain. Otherwise, the result ofdeblocking filtering the video data may be loop filtered so as to beused as a reference picture for compensating for motion of a subsequentpicture.

In the video encoding apparatus 1400 and the video decoding apparatus1500 employing deblocking filtering according to exemplary embodiments,a picture of an image is split into maximum coding units and each of themaximum coding units is encoded in coding units according to depths,which are individually determined. Thus, even adjacent coding units maybe different in terms of size or type.

In the video encoding apparatus 1400 and the video decoding apparatus1500 according to exemplary embodiments, a coding unit is not limited toa 16×16 macroblock and may be one of various sized or shaped blocks,e.g., 2×2, 4×4, 8×8, 16×16, 32×32, 64×64, 128×128, and 256×256 blocks.

In the video encoding apparatus 1400 and the video decoding apparatus1500 according to exemplary embodiments, each transformation unit is notlimited to a 4×4 or 8×8 block and may be one of various sized or shapedblocks, e.g., 2×2, 4×4, 8×8, 16×16, 32×32, 64×64, 128×128, and 256×256blocks. That is, maximum and minimum sizes of the transformation unitsare not limited.

In the video encoding apparatus 1400 and the video decoding apparatus1500 according to exemplary embodiments, prediction units for performingprediction coding and transformation units for performingtransforming/inverse transforming are separately set from among codingunits. Thus, a transformation unit may be larger than a prediction unit.The relationship between a coding unit, a transformation unit, and aprediction unit, according to an exemplary embodiment, has beendescribed above with reference to FIGS. 10 to 12.

In this disclosure, a boundary may be a boundary of a coding unit, aprediction unit, or a transformation unit. For example, a boundary maybe a common boundary of a coding unit and prediction unit, may be acommon boundary of a transformation unit and a prediction unit, or maybe a common boundary of a transformation unit and a prediction unit.Also, a boundary of a data unit may be a common boundary of all of acoding unit, a prediction unit, and a transformation unit. Also, aboundary of a predetermine data unit may be a boundary of a maximumcoding unit.

According to an exemplary embodiment, boundary characteristics areanalyzed so as to determine whether deblocking filtering is to beperformed on a boundary. For example, ‘disable_deblocking_filter_idc’defined in a slice header may be used to analyze the boundarycharacteristics. ‘disable_deblocking_filter_idc’ denotes a parameter fordetermining whether deblocking filtering is to be performed on aboundary of a slice. If ‘disable_deblocking_filter_idc’ is ‘1’,deblocking filtering may not be performed on the boundary of the slice.

For example, if ‘disable_deblocking_filter_idc’ is ‘1’ and a boundary isa boundary of a picture, then deblocking filtering is not performed on aboundary of a coding unit. Thus, if ‘disable_deblocking_filter_idc’ isnot ‘1’ and a boundary is not a boundary of a picture, then thedeblocking filtering performing units 1430 and 1540 may performdeblocking filtering on a boundary of a coding unit. If‘disable_deblocking_filter_idc’ is not equal to or is greater than ‘1’,deblocking filtering may be performed on a boundary of a prediction unitor a transformation unit.

In video encoding and decoding methods according to an exemplaryembodiment, a coding unit, a prediction unit, and a transformation unitare all separately set, and thus, a deblocking method may beindividually determined for each of the coding unit, the predictionunit, and the transformation unit according to boundary characteristicsthereof. Thus, in the video encoding apparatus 1400 and the videodecoding apparatus 1500 according to exemplary embodiments, a deblockingfiltering method may be set based on boundary characteristics of a dataunit.

For example, a deblocking filtering method for a boundary of a maximumcoding unit may be set. If a current boundary is a boundary of a maximumcoding unit, deblocking filtering may be performed on the currentboundary according to the deblocking filtering method for a boundary ofa maximum coding unit. A deblocking filtering method for a boundary of acoding unit may be set. If a current boundary is a boundary of a codingunit other than a maximum coding unit, deblocking filtering may beperformed on the current boundary according to the deblocking filteringmethod for a boundary of a coding unit.

A deblocking filtering method for a boundary of a transformation unitmay be set. If a current boundary is not a boundary of a maximum codingunit or a coding unit and is a boundary of a transformation unit,deblocking filtering may be performed on the current boundary accordingto the deblocking filtering method for a boundary of a transformationunit.

A deblocking filtering method for a boundary of a prediction unit may beset. If a current boundary is not a boundary of a maximum coding unit, acoding unit, or a transformation unit and is a boundary of a predictionunit, deblocking filtering may be performed on the current boundaryaccording to the deblocking filtering method for a boundary of aprediction unit.

A deblocking filtering method may include setting of whether deblockingfiltering is to be performed, the length of a deblocking filter, and thenumber and location of samples that are to be deblocking filtered.

According to an exemplary embodiment, the length of a boundary may varyaccording to the size or type of a coding unit, a prediction unit, or atransformation unit.

The relationship between a coding unit, a prediction unit, and atransformation unit according to other exemplary embodiments will now bedescribed with reference to FIGS. 18 to 20. In FIGS. 18 to 20, referencenumerals 1600, 1700, and 1800 denote coding units other than maximumcoding units.

FIG. 18 is a block diagram for describing the relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment. The coding unit 1600 is a 2N×2N block, andis prediction encoded on the basis of a prediction unit of an N×Npartition type and is transformed on the basis of an N×N transformationunit. Thus, boundaries 1612, 1614, 1616, 1620, 1626, 1630, 1632, and1634 are common boundaries of the coding unit 1600, prediction units,and transformation units, and boundaries 1618, 1622, 1624, and 1628 areboundaries of the prediction units and the transformation units.

The deblocking filtering performing units 1430 and 1540 of FIGS. 16 and17 may perform a deblocking filtering method for a boundary of a codingunit on the boundaries 1612, 1614, 1616, 1620, 1626, 1630, 1632, and1634 of the coding unit 1600 other than a maximum coding unit.

Otherwise, the deblocking filtering performing units 1430 and 1540 mayperform a deblocking filtering method for a boundary of a transformationunit on the boundaries 1618, 1622, 1624, and 1628 of the transformationunits other than the coding unit 1600 or a maximum coding unit.

FIG. 19 is a block diagram for describing a relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment. A coding unit 1700 is a 2N×2N block, andis prediction encoded based on a prediction unit of an N×N partitiontype and is transformed on the basis of a 2N×2N transformation unit.Thus, boundaries 1712, 1714, 1716, 1720, 1726, 1730, 1732, and 1734 arecommon boundaries of the coding unit 1700, prediction units, andtransformation units, and boundaries 1718, 1722, 1724, and 1728 areboundaries of only the prediction units.

The deblocking filtering performing units 1430 and 1540 of FIGS. 16 and17 may perform a deblocking filtering method for a boundary of a codingunit on the boundaries 1712, 1714, 1716, 1720, 1726, 1730, 1732, and1734 of the coding unit 1700 other than a maximum coding unit.

The deblocking filtering performing units 1430 and 1540 may perform adeblocking filtering method for a boundary of a prediction unit on theboundaries 1718, 1722, 1724, and 1728 of the prediction units other thana maximum coding unit, the coding unit 1700, or transformation units.

FIG. 20 is a block diagram for describing a relationship between acoding unit, a prediction unit, and a transformation unit, according toanother exemplary embodiment. A coding unit 1800 is a 4N×4N block, andis prediction encoded on the basis of a prediction unit of anasymmetrical partition type obtained by splitting the width of thecoding unit 1800 according to a ratio of 3:1 and is transformed on thebasis of a 2N×2N transformation unit. Thus, boundaries 1812, 1814, 1816,1820, 1822, and 1824 are common boundaries of the coding unit 1800,prediction units, and transformation units, a boundary 1818 is aboundary of only a prediction unit, and boundaries 1826, 1828, 1830, and1832 are boundaries of only transformation units.

The deblocking filtering performing units 1430 and 1540 of FIGS. 16 and17 may perform a deblocking filtering method for a boundary of a codingunit on the boundaries 1812, 1814, 1816, 1820, 1822, and 1824 of thecoding unit 1800 other than a maximum coding unit.

Also, the deblocking filtering performing units 1430 and 1540 of FIGS.16 and 17 may perform a deblocking filtering method for a boundary of atransformation unit on the boundaries 1826, 1828, 1830, and 1832 of thetransformation units other than a maximum coding unit or the coding unit1800.

Also, the deblocking filtering performing units 1430 and 1540 mayperform a deblocking filtering method for a boundary of a predictionunit on the boundary 1818 of the prediction unit other than a maximumcoding unit, the coding unit 1800, or the transformation units.

FIG. 21 illustrates a method of determining a deblocking filteringmethod, according to an exemplary embodiment. Deblocking filteringmethods may be set with respect to boundaries that satisfy a combinationof various conditions, respectively. For example, the various conditionsmay include types of data units that form a boundary, a prediction mode,whether a transformation coefficient that is not ‘0’ is present in ablock, a motion vector, a reference picture, the size of each of thedata units, and various encoding/decoding techniques applied to the dataunits. A deblocking filtering method may include setting of whetherdeblocking filtering is to be performed, the length of a deblockingfilter, and the number and location of samples that are to be deblockingfiltered.

For example, the deblocking filtering performing units 1430 and 1540 maydetermine an application unit 1930 that denotes a number of data unitsin which deblocking filtering is to be performed on boundaries thereof,based on a block type 1910 and a block size 1920 of two adjacent dataunits that form the boundary to be deblocking filtered, which aredefined in an encoding mode.

The number of data units in which deblocking filtering is to beperformed, i.e., the application unit 1930, may be determined to be ‘2’,‘1’, or ‘0’, based on whether the boundary between the two adjacent dataunits is a boundary of a maximum coding unit (LCU), a coding unit (CU),a prediction unit (PU), or a transformation unit (TU) (block type 1910)and whether the sizes of the two adjacent data units are the same, aregreater than a predetermined threshold or are not greater than thepredetermined threshold (block size 1920).

Also, a deblocking filtering method may be set to satisfy at least oneof the above conditions. For example, a different deblocking filteringmethod may be set for each of a plurality of the application units 1930related to a block boundary that satisfies a combination of conditionsof the block type 1910 and the block size 1920. Referring to FIG. 21, 36conditions of a target to be filtered may be determined according to acombination of the conditions of the block type 1910, the block size1920, and the application unit 1930. The deblocking filtering performingunits 1430 and 1540 may perform deblocking filtering by individuallydetermining deblocking filtering methods 1 through 36, based onconditions of a boundary that is to be deblocking filtered. That thedeblocking filtering methods 1 through 36 are determined means thatdifferent deblocking filtering methods are respectively set for 36boundary conditions. Thus, the same deblocking filtering method may beset for different boundary conditions. Also, the same deblockingfiltering method may be set for a group of boundary conditions. Forexample, the same deblocking filtering method may be set for blockboundaries of the same block type or may be set for block boundarieshaving the same size.

Although FIG. 21 illustrates only some deblocking filtering conditions,e.g., block type and block size of data units that form a boundary andthe number of data units that are to be deblocking filtered, thedeblocking filtering conditions may further include at least one of aprediction mode, such as an intra mode or an inter mode, whether anencoded residual component is present in a block, a motion vector, thenumber and index of reference pictures, and an encoding technique.

FIG. 22 illustrates samples 2000 that are to be deblocking filtered,according to an exemplary embodiment. From among the samples 2000,samples p3, p2, p1, and p0 are pixels present at a left side of a blockboundary, and the other samples q0, q1, q2, and q3 are pixels present ata right side of the block boundary. Although FIG. 22 illustrates thesamples 2000 arranged in a horizontal direction in which deblockingfiltering is performed, with respect to a vertical block boundary,deblocking filtering may be performed on samples arranged in a verticaldirection with respect to a horizontal block boundary.

According to an exemplary embodiment, boundary strength, whetherdeblocking filtering is to be performed, and the length of a deblockingfilter may be determined, based on the original values of the samples2000.

For example, boundary strength may be determined by the original valuesof the samples 2000. Whether deblocking filtering is to be performed onthe block boundary may be determined according to a combination ofconditions of the boundary strength and differences between the originalvalues of the samples 2000. Also, the length of a deblocking filter forthe samples 2000 and a number and locations of samples, the values ofwhich are changed when blocking filtering is performed, may bedetermined according to a combination of the conditions of the boundarystrength and the conditions of differences between the original valuesof the samples 2000.

According to an exemplary embodiment, if the boundary strength of thedeblocking filter for a luma component is ‘4’, results of deblockingfiltering the samples p2 and q2 may be disregarded from among thesamples 2000 used as deblocking filtering coefficients, except for thesamples p3 and q3.

According to an exemplary embodiment, the deblocking filteringperforming units 1430 and 1540 of FIGS. 16 and 17 may determine boundarystrength, whether deblocking filtering is to be performed, the length ofthe deblocking filter, and a number and location of samples that are tobe filtered, based on whether a current block boundary is a boundary ofa coding unit, a prediction unit, or a transformation unit.

FIG. 23 is a flowchart illustrating a method of encoding video by usingdeblocking filtering, according to an exemplary embodiment. Referring toFIG. 23, in operation 2110, a picture is split into maximum codingunits.

In operation 2120, coding units of coded depths, and an encoding modefor each of coding units, which is related to the coding units,prediction units, and transformation units, are determined with respectto each of the maximum coding units.

In operation 2130, deblocking filtering is performed on video data thathas been inversely transformed into a spatial domain in the codingunits, in consideration of the encoding modes for the coding units. Adeblocking filtering method that specifies whether deblocking filteringis to be performed on boundaries, boundary strength of a deblockingfilter, and filter tab size, may be determined according to types ofdata units including coding units, prediction units, and transformationunits that form the boundaries, the sizes of the data units, and apartition mode, defined in the encoding modes of the coding units.

FIG. 24 is a flowchart illustrating a method of decoding video by usingdeblocking filtering, according to an exemplary embodiment. Referring toFIG. 24, in operation 2210, a received bitstream is parsed to extract anencoding mode for each of coding units and video data that has beenencoded in the coding units.

In operation 2220, transformation coefficients are obtained by entropydecoding and inversely quantizing the encoded video data in the codingunits.

In operation 2230, video data in a spatial domain is reconstructed byinversely transforming the transformation coefficients in transformationunits and prediction decoding the transformation coefficients inprediction units, defined in the encoding modes for the coding units.

In operation 2240, deblocking filtering is performed on the video datain the spatial domain in consideration of the encoding modes for thecoding units. A deblocking filtering method that specifies whetherdeblocking filtering is to be performed on boundaries, boundary strengthof a deblocking filter, and filter tab size, may be determined accordingto types of data units including coding units, prediction units, andtransformation units that form the boundaries, the sizes of the dataunits, and a partition mode, defined in the encoding modes of the codingunits.

The exemplary embodiments can be written as computer programs and can beimplemented in general-use digital computers that execute the programsusing a computer readable recording medium. Examples of the computerreadable recording medium include magnetic storage media (e.g., ROM,floppy disks, hard disks, etc.) and optical recording media (e.g.,CD-ROMs, or DVDs).

While exemplary embodiments have been particularly shown and describedabove, it will be understood by those of ordinary skill in the art thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the inventive concept as definedby the appended claims. The exemplary embodiments should be consideredin a descriptive sense only and not for purposes of limitation.Therefore, the scope of the inventive concept is defined not by thedetailed description of the exemplary embodiments but by the appendedclaims, and all differences within the scope will be construed as beingincluded in the present inventive concept.

What is claimed is:
 1. A method of decoding video by using deblockingfiltering, the method comprising: hierarchically splitting a maximumcoding unit among one or more maximum coding units into one or morecoding units based on split information; determining one or moreprediction units in a coding unit among the one or more coding unitsusing partition type information, wherein the partition type informationindicates one of a symmetric type and an asymmetric type; determiningone or more transform units in the coding unit using size information ofa transform unit, wherein the transform unit among the one or moretransform units is rectangular with a horizontal size and a verticalsize indicated by the size information; performing prediction on aprediction unit among the one or more prediction units in the codingunit and inverse-transformation on the transform unit in the codingunit, in order to generate a reconstructed coding unit; when a boundaryincluded in the reconstructed coding unit corresponds to at least one ofa boundary of the prediction unit and a boundary of the transform unit,determining a boundary strength for the boundary included in thereconstructed coding unit based on at least one of non-zerotransformation coefficients, prediction mode, a motion vector, and areference index; and performing deblocking filtering on neighboringpixels according to the boundary strength, in order to generate afiltered coding unit including deblocking-filtered pixels.
 2. The methodof claim 1, wherein the prediction mode includes inter-prediction modeand intra prediction mode.
 3. The method of claim 1, wherein theboundary included in the reconstructed coding unit is one of a verticalboundary and a horizontal boundary.
 4. The method of claim 1, wherein:when the boundary included in the reconstructed coding unit is thevertical boundary, the neighboring pixels are located in a column withthe vertical boundary as a center, and the neighboring pixels includesleft side pixels (p3, p2, p1, p0) and right side pixels (q0, q1, q2,q3).
 5. The method of claim 1, wherein the filtered coding unitincluding the deblocking-filtered pixels is used as a reference picturefor motion-compensation of another picture.